Summer's greatest unwritten rule may just be this — no look is complete without a killer pair of shades. If you've doubted the potential they have to lend polish, cool, and even finish an otherwise undone look, the proof is in this batch of celebrity street stylers. Armed with their sunglasses of choice, each of these celebs proves that eyewear may just be the easiest way to up the ante on any look, period. Click through the celebrity lookbook for all the inspiration — then shop the styles for yourself.